Abrasive blasting machine

ABSTRACT

An improved abrasive blasting machine comprises radially extending throwing blades mounted on a wheel by means of blade blocks. Each blade block has a first groove near an inner end of the block and a second groove near an outer end. Each blade includes lugs for insertion in the grooves. The improved blasting machine includes a centrally disposed impeller which restricts the movement of the blades, particularly in a radial direction. Preferably, this is accomplished by employing an impeller having a shoulder which contacts the inner ends of the blades.

United States Patent [191 Golf Feb. 25, 1975 1 ABRASIVE BLASTING MACHINE[76] Inventor: James R. Goff, 6601 Shawnee Dr.,

Oklahoma City, Okla. 73116 [22] Filed: May 13, 1974 [21] Appl. No.:469,567

[52] US. Cl. 51/9 R, 241/275 [51] Int. Cl. B24c 5/06 [58] Field ofSearch 51/9 M; 241/275, 300

[56] References Cited UNITED STATES PATENTS 2,376,639 5/1945 Unger 5l/9R 2,392,958 l/l946 Tice 241/275 X 2,991,949 7/1961 Sellars 241/300 X3,093,329 6/1963 Bridgewater.... 241/275 3,540,667 11/1970 Parker241/275 3,606,182 9/1971 Warren 241/275 Primary ExaminerDonald G. Kelly[57] ABSTRACT An improved abrasive blasting machine comprises radiallyextending throwing blades mounted on a wheel by means of blade blocks.Each blade block has a first groove near an inner end of the block and asecond groove near an outer end. Each blade includes lugs for insertionin the grooves. The improved blasting machine includes a centrallydisposed impeller which restricts the movement of the blades,particularly in a radial direction. Preferably, this is accomplished byemploying an impeller having a shoulder which contacts the inner ends ofthe blades.

10 Claims, 6 Drawing Figures PATENTEI] FEBZ 5 i975 SHEET 3 UF 3 ABRASIVEBLASTING MACHINE sometimesreferred to as throwing blades. Due to theaction of the abrasive material on the throwing blades, the bladesexhibit considerable wear over a period of time. Attempts have been madeto fabricate the blades from abrasion resistant alloys. In other cases,special blade configurations are employed to minimize the effects of theabrasive material.

Notwithstanding these attempts to minimize wear and extend the life ofthe throwing blades, periodic blade removal and replacement isnecessary. This results in a loss of valuable operating time.Furthermore, while the blades must be removable, they must also be heldso securely that they will resist the tremendous centrifugal forcesexerted on them when the wheel is operating.

' ends and front and rear surfaces. The inner ends of the There are twocommon methods for securing the maintained in a spaced apart relation.Longitudinal narrow edges of the throwing blades are generally insertedinto radial grooves arranged in opposing surfaces of the two disks.Auxiliary means, such as bolts, pivotal locking means, eccentrics, etc.,can be employed to secure the blades against radial displacement.

The conventional methods for blade removal, therefore, involve the useof a separate securing element, typically a bolt, or relative movementbetween surfaces by sliding a blade into or out of a groove in a wheeldisk. The exposed portions of the securing elementsin these devices aresusceptible to abrasion and disfiguration by fine particles of theabrasive material. This abrasive material can also enter open cracks andcrevices, and within a relatively short time jam or freeze the securingelements or throwing blades in their grooves. In such instances, removalof the blades can only be accomplished with considerable effort and lossof production time.

Thus, there exists a need in the art for an improved centrifugalblasting machine in which the throwing blades are securely mounted onthe throwing disk or disks to prevent movement of the blades, especiallyin a radial direction. The improved centrifugal blasting machine shouldalso provide for easy removal and replacement of the throwing bladeswithout the need for special tools and auxiliary securing elements. Theblades should be easily removable even after extended use in, anatmosphere containing fine particles of the abrasive material.

Accordingly, this invention provides an improved rotatable, centrifugal,abrasive blasting device. The device comprises a driven wheel and aplurality of circumferentially spaced, radially extending blades mountedon the wheel. The blades have inner and outer blades define a centralopening when mounted on the wheel. A hollow, vaned, driven impeller ismounted in the central opening for rotation with the wheel. Astationarycontrol cage surrounds the impeller. The control cage has anopening therein for the discharge of abrasive material from the impelleronto the throwing blades. The device also comprises means for feedingparticulate, abrasive material to the impeller. The improvementcomprises mounting the blades on the wheel by means of blade blocks. Theblade blocks have inner and outer ends. Each of the blade blocks has afirst groove proximate its inner end and. a second groove proximate itsouter end. Each of the blades has a first lug on its inner, rear surfacefor insertion in said first groove of a blade block. Each blade also hasa second lug on the rear surface and intermediate the ends of the blade.This second lug is adapted for insertion in said second groove of ablade block. Radial movement of the blades issubstantially prevented bythe impeller. This is conveniently and preferably accomplished byemploying an impeller having a shoulder which contacts the inner ends ofthe throwing blades.

This invention will be more fully understood from the detaileddescription which follows, and by reference to the accompanying drawingswhich depict a centrifugal blasting machine according to this inventionand detailed views of its various parts. In the drawings:

FIG. 1 is a plan view of a throwing wheel having a blade block andthrowing blade installed thereon;

FIG. 2 is a view of a preferred configuration for a throwing bladeblock;

FIG. 3 is a view of a preferred configuration for a throwing blade;

FIG. 4 is a detail view of the central portion of a blasting machine;

FIG. 5 is a view in perspective of a preferred, but optional, bladeretainer clip; and

FIG. 6 is a view in perspective of a preferred impeller.

Referring to FIG. 1, there is depicted a wheel or disk generallydesignated as l. The wheel has a plurality of holes 2 uniformly spacedcircumferentially. Holes 2 are adapted for the insertion of boltsemployed to secure blade blocks to the wheel 1. Preferably, the wheel 1has an opening 3 centrally disposed therein and of a size sufficient toaccommodate a portion of the impeller. Shown in FIG. I is a blade block4 and blade 5 in a typical position on the wheel 1. The blade block 4and blade 5 will be described in greater detail hereinafter.

The portion of the device depicted in FIG. 1 is adapted for rotation ina clockwise direction. The blade 5 shown in the FIGURE is curved in thedirection of rotation. Other blade configurations can be employed. Forexample, a substantially straight blade or blade having a differentcurvature would be satisfactory.

Referring to 'FIG. 2, there is depicted a preferred blade block employedin the device of this invention. The blade block, generally designatedas 4, has two drilled and tapped holds 6 and 7 therein. Blade block 4can be secured to wheel 1 by inserting bolts through holes 2 in wheel 1into holes 6 and 7 in blade block 4. Blade block 4 has an inner end 8and an outer end 9. A first groove 10 is provided in the blade blockproximate the inner end 8. Proximate the outer end 9 there is provided asecond groove 11 and a cavity 11.

In FIG. 3, there is depicted a preferred blade employed in the device ofthis invention. The blade, generally designated as 5, comprises athrowing surface 12 which corresponds to the front surface of the blade.The blade also has a rear surface 13, an outer end 14 and an inner end15. The inner end 15 is depicted as a curved surface. Preferably, thecurvature ofinner end 15 is such that its entire surface willsubstantially correspond to the curvature of the impeller against whichit abuts after the blasting machine has been assembled.

'The blade has a lug 16 near its inner end 15. Intermediate the outerend 14 and inner end 15 of blade 5 is a second lug 17 on the rearsurface 13 of the blade. Lug 16 aids in preventing the movement of theblade radially outward once the blasting machine has been assembled. Lug17 aids in the assembly of the device, and provides support in adirection substantially normal to the length of the blade. The lug 16 isadapted for insertion into the first groove in blade block 4. The lug 17is adapted for insertion into the second groove 11 in blade block 4.

Referring next to FIG. 4, there is depicted a detailed view of thecentral portion of a blasting machine of this invention. The wheel 1 hasmounted thereon throwing blades 5 by means of blade blocks 4. The innerends of the blades 5 define a central opening 18. Inserted in theopening 18 is a hollow, vaned impeller 19 having a bolt hole 20 therein.Surrounding the impeller 19 is a control cage 21 having an opening (notshown) therein for the passage of abrasive material from the impeller 19onto the blades 5. The device also includes means for feedingparticulate, abrasive material to the impeller. This feeding means isshown in FIG. 4 as a feed spout 22. A cage retainer 23 and cage adapter24 secure the control cage 21 within the blasting machine in aconventional manner.

The wheel is driven by a motor (not shown) having a motor shaft 25. Ahub 26 is mounted on shaft 25 by means of a conventional centertaper-lock bushing (not shown in the FIG). The hub 26 includes boltholes shown as 27 in the FIGURE. The wheel I is installed on the hub 26,and bolt hole 27 on the hub is aligned with a bolt hole 2 on the wheel.Blade blocks 4 are then installed so that holes 6 and 7 in the bladeblock are aligned with holes 2 in the wheel 1. The blade blocks 4 canthen be bolted to the hub-wheel assembly.

Blades 5 are installed on the blade blocks 4. The impeller 19 isinserted in the central opening 18. Preferably, a wheel 1 having anopening 3 is employed, and the impeller 19 projects at least partiallyinto this opening as shown in FIG. 4. The impeller 19 preferably has aslot cast into its face, which interfaces with a pilot hole machined inthe vertical surface 38 of the hub to thereby center the impeller 19within wheel 1 and opening 3. A pin can be inserted in the hub pilot.The pin projects from the face of the hub and aligns with the slot castinto the impeller 19. This pin not onlyaligns the impeller slot with thehub pilot, but also provides a positive means of driving the impellerwith the hubwheel assembly. The pilot holes and pin are not shown in theFIGURES. To complete the assembly, a bolt 28 is inserted through opening20 in impeller 19 and into a threaded opening 29 in motor shaft 25. Ahub seal and retainer 30 can be installed in a conventional manner.

In the device of this invention, the impeller retards radial movement ofthe blades. FIG. 4 depicts the preferred embodiment in which the wheel 1has a central opening 3 into which a portion of the impeller 19projects. As shown in the FIGURE, a shoulder 31 locks the blade inposition. Each blade 5 is thereby prevented from moving radially inwardtoward the impeller. Because the lug 16 on blade 5 (see FIG. 3) engagesthe groove 10 in blade block 4 (see FIG. 2), the shoulder 31 on impeller19 effectively locks the lug 16in groove 10 thereby preventing movementof each blade 5 in a direction radially outward from the impeller. Thus,it will be apparent that blade 5 is securely locked in position.

While the impeller 19 is shown with a shoulder 31 which obstructsmovement of blades 5, it will be apparent that other modes ofconstruction are possible. For example, the impeller could be mounted onthe surface 32 of the wheel 1; that it, wheel 1 would not have acentrally disposed opening 3. In this event, the impeller would stillobstruct the movement of blades 5.

In a preferred embodiment of this invention, assembly of the blades tothe blade blocks can be facilitated by employing a blade retainer clip.A preferred clip is shown in FIG. 5. The clip in FIG. 5 is generallydesignated as 33. Blade retainer clip 33 comprises a substantially flatportion 34 which terminates in a curved portion 35. The clip 33 has alug 36 protruding from its rear surface 37. The lug 36 can beconveniently provided by stamping or punching it out of thesubstantially flat portion 34 so that at least one end of the lug isstill secured to the flat portion.

The blade retainer clip 33 is secured to lug 17 of blade 5 (see FIG. 1).This can conveniently be accomplished by means of an adhesive or a tape.The lug 36 of retainer clip 33 is inserted in cavity 1 l of blade block4. While the use of a blade retainer clip is an optional embodiment ofthis invention, the clip is an assembly convenience which enables theworker to temporarily retain the blade on the blade block until theremainder of the blades are installed. Once the device of this inventionhas been assembled, the blade retainer clips are no longer required.Thus, should they inadvertently become detached from the device, no harmwill generally be done since the blades are locked on the wheel by meansof lugs (16 and 17) and the interference provided by the impeller (e.g.,shoulder 31). When a blade retainer clip is not employed, it is notnecessary to provide blade block 4 with a cavity 11' since the functionof cavity 11 is to provide a recess for lug 36 of blade retainer clip33.

When a blade retainer clip such as 33 is employed, the blade 5 isassembled to the blade block 4 by inserting the lug 16 in the groove 10,and then pivoting the blade rearward until lug 17 of the blade is withingroove 11 and the lug 36 of the retainer clip is inserted into cavity11'.

As previously noted, use of the blade retainer clip is an optionalembodiment. If a blade retainer clip is not employed, the lug 17 can betemporarily secured in groove 11 in blade block 4 by the use of anadhesive or a tape. The blade retainer clip is preferred, however, sinceit not only retains the blade in position, but aids in the alignment ofthe lug 17 and groove 11.

To remove the blades 5 from the device, first the feed spout 22 isdetached from the machine or otherwise moved free of the central opening18. Control cage 21 is then withdrawn. The impeller 19 can then beremoved after loosening and removing bolt 28. A sharp blow from a hammeror other tool will break the small retainer clip, thereby entirelyfreeing the blade 5.

While centrifugal blasting machines can be driven by means of a beltconnected to a motor, direct connection to a motor shaft is now the morecommon method. Standard commercially available motors generally have afloating motor shaft; that is, the shaft moves inward and outward in alongitudinal direction. Typically, the shaft will be capable of movingabout 0.25 inches. When the motor is operating, longitudinal movement ofthe motor shaft will generally be inward. When the motor is off and theshaft is in a relaxed position, the shaft will generally be extendedoutward. In centrifugal blasting machines of the prior art, it wasgenerally necessary to provide the motor shaft with a locked bearingwhich would prevent longitudinal movement of the shaft. The use of alocked bearing adds to the cost of the machine. The locked bearing wasrequired to prevent longitudinal movement of the impeller because thecontrol cage at least partially surrounded or wrapped around theimpeller, and movement ofthe motor shaft in a longitudinal directionwould cause the control cage to interfere with the impeller when theimpeller was directly connected to the motor shaft.

These problems are alleviated by the preferred impeller and control cageemployed in this invention. Re-

- ferring to FIG. 4, it is seen that the control cage 21 does not wraparound the surface 39 of the impeller 19. Thus, when the impeller 19 andmotor shaft move inward and outward in a longitudinal direction, thereis no interference between the control cage 21 and impeller 19. Thus, astandard commercial motor with a floating motor shaft can be employed inthe device of this invention.

In prior art centrifugal blasting machines, a centering plate wasrequired between the impeller and bare wheel. In the preferred device ofthis invention, however, the centering plate and impeller comprise onepiece. This is advantageous because the control cage and impeller can bemolded separately using simple foundry practice. Casting techniques aresimpler because the parts can be cast without the use of cores.

A preferred impeller 19 employed in this invention is shown in FIG. 6.It comprises a plurality of fingers 40 which extend ina longitudinaldirection. The outer most ends 451 of the fingers 40 are not connectedto each other, thereby forming openings 42 between the fingers 40. Thisis advantageous because the fingers are immediately adjacent the feedspout when the centrifugal blasting machine is assembled. This isreadily apparent from FIG. 4 where it is seen that the space between theimpeller 19 and the feed spout 22 is very small. This makes it possibleto feed relatively large quantities of abrasive material to the impellersince the fingers on the impeller pick up the abrasive material as soonas the material leaves the feed spout. Tnat is, the abrasive materialfrom the feed spout drops directly onto the fingers, and the fingersthen project-the abrasive onto u the throwing blades. This featureshould'be contrasted.-

abrasive material.

A further preferred embodiment ofthis invention can be seen in FIG. 4.The fingers of the impeller 19 define a central opening 43 into whichabrasive from feed spout 22 falls. The floor 44 of this central opening43 separates opening 43 from a second central opening 45. This secondcentral opening 45 is such that motor shaft 25 can be inserted therein.When the centrifugal blasting machine is assembled, motor shaft 25 abutsfloor 46 of central opening 45. Since standard, commercial motors of agiven size have motor shafts of the same length, an impeller having asecond central opening 45 makes it possible to mount the impeller closerto the motor. Typically, motor shaft 25 can project into the secondcentral opening 45 about 1 inch. It will immediately be apparent thatthis arrangement brings the mass of the impeller closer to the bearingin the motor. This reduces the overhung load on the bearing, therebyreducing the stress on the bearing. This minimizes bearing wear.

There are a number of advantages associated with the device of thisinvention. First of all, means are provided for rigidly securing athrowing blade to a blasting wheel. Movement of the blades in a radialdirection is substantially prevented. Equally important, the blades canstill be removed relatively easily. Special blade retainers and bladesecuring means need not be used each time the blades are changed.Special assembly and disassembly tools are not required. The blades donot become wedged or frozen in the wheel, such as will frequently occurwhen dovetail or other grooves are employed. The ease of assembly anddisassembly minimizes the time required to change worn blades, therebyminimizing lost production time. The blades can be removed easily evenafter extended use in an atmosphere containing fine particles of theabrasive material. The preferred impeller in which the impeller andcentering plate comprise one piece can be cast in a relatively simplemanner. The preferred impeller comprising a plurality of discretefingers provides for the uniform flow of abrasive material to thethrowing blades. The preferred impeller which has an opening therein forinsertion of at least a portion of the shaft of the blasting machinedrive motor minimizes wear on the bearing for the motor shaft.

What is claimed is:

1. In a rotatable centrifugal abrasive blasting device comprising adriven wheel; a plurality of circumferentially spaced radially extendingblades mounted on said wheel, said blades having inner and outer endsand front andrear surfaces; said inner ends of said blades defining acentral opening; a hollow, vaned, driven impeller mounted in saidcentral opening rotatable with said wheel; a stationary control cagearound said impeller, said control cage having an opening therein forthe passage of abrasive material from said impeller onto said blades;and means for feeding particulate, abrasive material to said impeller;the improvement wherein said blades are mounted on said wheel by meansof ,.-blade blocks on said wheel; said blade blocks having ,said block;and further wherein said impeller obstructs movement of said blades in adirection radially inward.

2. A centrifugal blasting device according to claim 1 in which the wheelhas an opening centrally disposed therein and said impeller protrudesinto said opening in said wheel, and vfurther wherein said impeller hasa shoulder which locks the blades to the blade blocks.

3. A centrifugal blasting device according to claim 1 inwhich each ofsaid second grooves is provided with a cavity, and a bladeretainerclipis secured to said second lug, said clip being secured in said cavity.

. 4. A centrifugal blasting device according to claim 2 in which theimpeller abuts a surface of a hub which connects the wheel to the shaftof a motor, said hub having a pilot hole machined in a surface thereoffor alignment with'a pilot hole in the impeller, and a pin connects thepilot hole in the hub to the pilot hole in the impeller.

5. A centrifugal blasting device according to claim 1 in which saiddevice includes a centering plate which together with the impellercomprise one piece.

6. A centrifugal blasting device according to claim 1 in which theimpeller has a plurality of discrete fingers having openingstherebetween, said fingers defining a 'central opening for receivingabrasive material from said feeding means.

7. A centrifugal blasting device according to claim 1 in which saiddevice is driven by a motor having a motor shaft, said impeller isconnected to said motor shaft and said impeller has an opening thereinfor insertion of a portion of said shaft.

8. A centrifugal blasting device'according to claim 3 in which saiddevice includes a centering plate which together with the impellercomprise one piece.

9. A centrifugal blasting device according to claim 8 in which theimpeller has a plurality of discrete fingers having openingstherebetween, said fingers defining a central opening for receivingabrasive material from said feeding means.

10. A centrifugal blasting device according to claim 9 in which saiddevice is driven by a motor having a motor shaft, said impeller isconnected to said motor shaft and said impeller has an opening thereinfor insertion of at least a portion of of said shaft.

1. In a rotatable centrifugal abrasive blasting device comprising adriven wheel; a plurality of circumferentially spaced radially extendingblades mounted on said wheel, said blades having inner and outer endsand front and rear surfaces; said inner ends of said blades defining acentral opening; a hollow, vaned, driven impeller mounted in saidcentral opening rotatable with said wheel; a stationary control cagearound said impeller, said control cage having an opening therein forthe passage of abrasive material from said impeller onto said blades;and means for feeding particulate, abrasive material to said impeller;the improvement wherein said blades are mounted on said wheel by meansof blade blocks on said wheel; said blade blocks having inner and outerends; each of said blade blocks having a first groove proximate itsinner end and a second groove proximate its outer end; each of saidblades having a first lug on its inner, rear surface for insertion insaid first groove of said block, and a second lug on the rear of eachblade, said second lug intermediate the ends of the blade for insertionin said second groove of said block; and further wherein said impellerobstructs movement of said blades in a direction radially inward.
 2. Acentrifugal blasting device according to claim 1 in which the wheel hasan opening centrally disposed therein and said impeller protrudes intosaid opening in said wheel, and further wherein said impeller has ashoulder which locks the blades to the blade blocks.
 3. A centrifugalblasting device according to claim 1 in which each of said secondgrooves is provided with a cavity, and a blade retainer clip is securedto said second lug, said clip being secured in said cavity.
 4. Acentrifugal blasting device according to claim 2 in which the impellerabuts a surface of a hub which connects the wheel to the shaft of amotor, said hub having a pilot hole machined in a surface thereof foralignment with a pilot hole in the impeller, and a pin connects thepilot hole in the hub to the pilot hole in the impeller.
 5. Acentrifugal blasting device according to claim 1 in which said deviceincludes a centering plate which together with the impeller comprise onepiece.
 6. A centrifugal blasting device according to claim 1 in whichthe impeller has a plurality of discrete fingers having openingstherebetween, said fingers defining a central opening for receivingabrasive material from said feeding means.
 7. A centrifugal blastingdevice according to claim 1 in which said device is driven by a motorhaving a motor shaft, said impeller is connected to said motor shaft andsaid impeller has an opening therein for insertion of a portion of saidshaft.
 8. A centrifugal blasting device according to claim 3 in whichsaid device includes a centering plate which together with the impellercomprise one piece.
 9. A centrifugal blasting device according to claim8 in which the impeller has a plurality of discrete fingers havingopenings therebetween, said fingers defining a central opening forreceiving abrasive material from said feeding means.
 10. A centrifugalblasting device according to claim 9 in which said device is driven by amotor having a motor shaft, said impeller is connected to said motorshaft and said impeller has an opening therein for insertion of at leasta portion of of said shaft.